From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate001.proxmox.com (gate001.proxmox.com [IPv6:2a0f:8001:1:32::40]) by lore.proxmox.com (Postfix) with ESMTPS id 23A0C1FF0E4 for ; Tue, 14 Jul 2026 14:45:02 +0200 (CEST) Received: from gate001.proxmox.com (localhost.localdomain [127.0.0.1]) by gate001.proxmox.com (Proxmox) with ESMTP id 49222213E7; Tue, 14 Jul 2026 14:45:01 +0200 (CEST) From: Dominik Csapak To: pve-devel@lists.proxmox.com Subject: [PATCH] kernel config: don't automatically enable kexec handover (KHO) Date: Tue, 14 Jul 2026 14:44:46 +0200 Message-ID: <20260714124456.347992-1-d.csapak@proxmox.com> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SPAM-LEVEL: Spam detection results: 0 AWL 0.349 Adjusted score from AWL reputation of From: address DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment (newer systems) RCVD_IN_DNSWL_LOW -0.7 Sender listed at https://www.dnswl.org/, low trust SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Message-ID-Hash: B2KUINKGL4U33KSVNXJQZW3E2LR32IYU X-Message-ID-Hash: B2KUINKGL4U33KSVNXJQZW3E2LR32IYU X-MailFrom: d.csapak@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox VE development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT is enabled by default in the upstream ubuntu kernel config, but has a (probably) unintended side-effect: when KHO is automatically enabled, the kernel reserves scratch memory for the kernel handoff and marks it with MIGRATE_CMA to prevent non-movable allocations there. This causes unusual stats in /proc/meminfo, for example: CmaTotal: 0 kB CmaFree: 4894720 kB which looks nonsensical on the surface. It also reduces the available memory for e.g. guests with PCI passthrough, as pinner memory can't live in these areas. Since we don't use kexec handover by default, and it can still be enabled on the kernel commandline (kho=on), disable it by default to increase the available pinnable memory for guests. Signed-off-by: Dominik Csapak --- debian/rules.d/config-common.opts | 1 + 1 file changed, 1 insertion(+) diff --git a/debian/rules.d/config-common.opts b/debian/rules.d/config-common.opts index 64505b4..204bab4 100644 --- a/debian/rules.d/config-common.opts +++ b/debian/rules.d/config-common.opts @@ -68,3 +68,4 @@ -d CONFIG_N_GSM -d UBSAN_BOUNDS -e CONFIG_RUST +-d CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT -- 2.47.3